High‐Entropy Spinel Oxide Nanofibers as Catalytic Sulfur Hosts Promise the High Gravimetric and Volumetric Capacities for Lithium–Sulfur Batteries

Abstract

The exploration of new catalytic hosts is highly important to tackle the sluggish electrochemical kinetics of sulfur redox for achieving high energy density of lithium–sulfur batteries. Herein, for the first time, we present high‐entropy oxide (HEO, (Mg0.2Mn0.2Ni0.2Co0.2Zn0.2)Fe2O4) nanofibers as catalytic host of sulfur. The HEO nanofibers show a synergistic effect among multiple metal cations in spinel structure that enables strong chemical confinement of soluble polysulfides and fast kinetics for polysulfide conversion. Consequently, the S/HEO composite displays the high gravimetric capacity of 1368.7 mAh g−1 at 0.1 C rate, excellent rate capability with the discharge capacity of 632.1 mAh g−1 at 5 C rate, and desirable cycle stability. Furthermore, the S/HEO composite shows desirable sulfur utilization and good cycle stability under a harsh operating condition of high sulfur loading (4.6 mg cm−2) or low electrolyte/sulfur ratio (5 μL mg−1). More impressively, the high volumetric capacity of 2627.9 mAh cm−3 is achieved simultaneously for the S/HEO composite due to the high tap density of 1.92 g cm−3, nearly 2.5 times of the conventional sulfur/carbon composite. Therefore, based on high‐entropy oxide materials, this work affords a fresh concept of elevating the gravimetric/volumetric capacities of sulfur cathodes for lithium–sulfur batteries.

Nickel–Platinum Alloy Nanocrystallites with High‐Index Facets as Highly Effective Core Catalyst for Lithium–Sulfur Batteries

“…Furthermore, the dissolution behaviors of Li 2 S on different matrices are investigated by potentiostatic charge tests. [67,68] For CNC Ni-Pt electrode, the interconnected ion channels in the uniform and porous settled layer are beneficial for the coupled conversion of solid sulfides to soluble LiPS when charging, thus the working electrode can recover to the original state without distinguishable bulk "dead sulfur" remained (Figure 6l). In the case of NC Ni-Pt and bare carbon paper electrodes, the lumpish deposits generated at the discharge stage retard the solid-liquid conversion.…”

Sol-gel-derived Ordered Mesoporous High Entropy Spinel Ferrites and Assessment of their Photoelectrochemical and Electrocatalytic Water Splitting Performance

“…[68,69] In this context, Stenzel et al identified an improved (equiatomic) elemental composition for spinel-structured HEOs resulting in low overpotentials of 293 mV (at 10 mA/cm 2 ). [69] High entropy ferrites (HEF) have recently been investigated as highperforming sulfur host material in lithium-sulfur batteries, [70] as microwave absorbing material, [71,72] and magnetic insulator, [73] however, up to now, never in the context of electrocatalytic and/or photoelectrochemical water splitting. Recently, the group of Brezesinski has reported on mesoporous ferrite films as well, however incorporating fewer types of cations and focusing on magnetic properties.…”

“…In literature, the (CoNiCuZnMg)Fe2O4 system was already proven to form highly robust entropically stabilized structures with notable properties. [70] These data imply the need for further characterization of this novel material in order to draw a detailed picture about the fundamental physicochemical properties providing information about possible and expected surface electron transfer reactions and opening up not only potential application fields in the frontier of electrocatalysis, but also for any other surface-related energy technology.…”

Polymers in Lithium–Sulfur Batteries

“…In the last years, most investigations on LSBs have mainly focused on the design and modification of sulfur cathodes. [13,14,[25][26][27] Since Ji et al [28] reported the carbon/sulfur composite cathode by using mesoporous carbon as the sulfur carrier in 2009, tremendous sulfur-based composites cathodes with carbonaceous materials, [29] metal compounds, [30] and metal-organic frameworks [31] as carriers have been recently demonstrated to address the aforementioned issues. The elaborated carbon architectures can not only promote the electronic conductivity of the sulfur cathode, but also realize spatial confinement of active materials and LiPS in nanopores.…”